1. Field of the Invention
The invention concerns an airflow unit, especially a filter fan or discharge filter with or without a fan for installation in an installation opening in a wall, especially a housing for components that produce waste heat, such as a switch cabinet, electronics cabinet, computer system, or the like.
2. Description of the Related Art
When a housing contains components that produce a sufficiently large amount of waste heat, it is necessary to eliminate the waste heat from the housing and to control the temperature in the housing by blowing or drawing a suitable amount of ambient air into the interior of the housing by means of the fan. Computer housings are a well-known example of this. Housings of this type are usually equipped with a filter fan, which either runs continuously or is switched on and off by a control unit as a function of the temperature in the housing. The filter fan is installed in a recess of a wall of the housing and is secured, for example, by screw connections. At the same time, corresponding air discharge slits are provided elsewhere on the housing to allow the air to be discharged. However, the installation of filter fans of this type is often laborious, since, when screw connections are used, hardly any clearance is available even for subsequent visual alignment of the filter fan.
The object of the present invention is to develop an airflow unit as a filter fan or discharge filter of the type described above with an improved shielding effect with high operational security of an electrically conductive connection between an EMC shielding plate and an installation opening of a switch cabinet and in regard to EMC stability in conjunction with high IP protection. In addition, opening compatibility with known, previously used filter fans and simple, cost-effective installation and production should be achieved.
This objective is achieved with an airflow unit of the type described at the beginning, which comprises
a ventilation grating, which consists of a frame with a front plate provided with strips and/or air slits and a neck-like recessed insert, such that the frame holds a filter medium,
a support member, which consists of a frame with a peripheral wall surface that preferably expands outwardly like a wedge and with an interior space for holding the neck-like recessed insert of the ventilation grating, such that the support member, on its side facing away from the ventilation grating, is provided with airflow openings and with water-diverting fins or rib formations for draining splash water and condensation water that have penetrated the unit and serves to hold the neck-like recessed insert of the ventilation grating,
a shielding grating with an EMC seal for EMC damping, which is inserted in the support member on the side facing away from the ventilation grating and is held on the support member by means of screw, rivet, adhesive, or clamp connections, and
and an IP seal foamed onto the support member for protection against splash water and spray water, such that all components of the airflow unit are held together by clamp or screw connections, and such that, to install the airflow unit in the region of the installation opening in the wall surface of the housing, the airflow unit is placed on the outer wall surface of the wall of the housing and is preferably detachably connected with the housing wall.
This airflow unit is simple to produce and easy to install. A very good shielding effect with respect to EMC stability is achieved, together with high IP protection. Without a fan, the airflow unit can be used, for example, as an air discharge filter in switch cabinets. With a fan, the airflow unit is used as a filter fan, especially in housings that contain components that generate waste heat. In this regard, the fan can be premounted on the components of the airflow unit. The fan may be used for air suction or air exhaust. The complete unit is then installed on the wall of the cabinet from the outside, and the opening in the cabinet wall must be dimensioned in such a way that the fan can be pushed through it.
A chamfered outer wall surface of the support member produces the advantage that splash water drains easily. In addition, the chamfered outer wall surface makes it possible to countersink fastening screws, since recesses are formed in the peripheral regions.
A second embodiment of a airflow unit of the invention in accordance with FIG. 2 comprises
a design cover, which consists of a frame with a front plate provided with strips and/or air slits and with a neck-like recessed insert,
a space-filling filter medium, which is inserted in the space bounded by the frame,
a base housing, which consists of a frame with a peripheral sidewall and with an interior space for holding the neck-like recessed insert of the design cover, such that the base housing is provided with airflow openings on its side that faces away from the design cover and that forms the rear wall and with a peripheral seal on its side facing the design cover and has at least two locking corners.
an EMC shielding plate, which consists of a metal frame with a peripheral sidewall, whose corner regions have recesses for the locking corners of the base housing, and with a rear wall designed as a shielding grating, such that the lateral edges of the peripheral sidewall of the metal frame which face the base housing have a number of spring contact tongues for producing an electrically conductive connection between the EMC shielding plate and the installation opening of a switch cabinet, which spring contact tongues have end sections that are laterally turned out from the plane formed by the peripheral sidewall of the metal frame, such that the contact tongues are fastened to the metal frame or are cut out of the peripheral sidewall of the metal frame, such that all of the components of the airflow unit are held together by clamping, riveting or screw connections, and such that, to install the airflow unit in the area of the installation opening, the sidewalls of the base housing of the airflow unit are placed on the outside wall surface of the wall of the housing and preferably detachably connected with it.
An airflow unit designed in this way is simple to produce and easy to install. A very good shielding effect is achieved in regard to EMC stability in conjunction. Without a fan, the airflow unit can be used, for example, as an air discharge filter in switch cabinets. With a fan, the airflow unit is used as a filter fan, especially in housings that contain components that generate waste heat. In this regard, the fan can be premounted on the components of the airflow unit. The fan may be used for air suction or air exhaust. The complete unit is then installed on the wall of the cabinet from the outside, and the opening in the cabinet wall must be dimensioned in such a way that the fan can be pushed through it.
Due to the special design of the EMC shielding plate of the peripheral sidewall of the frame that forms the EMC shielding plate, an excellent shielding effect is guaranteed, since a good electrically conductive connection is created between the EMC shielding plate and the installation cutout of the switch cabinet. Even if the dimensions of the installation cutout deviate from the dimensions of the airflow unit, good contact is ensured, since the spring contact tongues adapt to differences in dimensions.
In addition, a high degree of IP protection is achieved with the airflow unit of the invention; cost-effective manufacture and installation is also assured, as is good contacting of the spring contact tongues with the installation wall of the switch cabinet. Due to the large number of contact tongues provided on the EMC shielding plate, which are arranged in the form of strips, contact with the metal surfaces of the switch cabinet is always guaranteed.
When the airflow unit is used with a fan, a fan housing with a fan and possibly with a protective safety grille on the outside is joined with the design cover, the base housing, and the EMC shielding plate.
The components of the airflow unit are mounted on the wall of the design cover from the outside by screws or fastening devices of a different design.
Except for the EMC shielding plate, all of the components of the airflow unit are made of a plastic.
In accordance with another refinement of the invention, to be able to use fans of different sizes in the airflow unit, an adapter-like fan support is installed between the fan housing with the fan and the other components of the airflow unit for mounting fan housings with larger or smaller dimensions relative to the components of the airflow unit.
Another advantage is achieved with a refinement of the airflow unit, in which the shielding grating of the EMC shielding plate is provided with surfaces running at an inclination from the peripheral edge of the shielding grating to its center to form a concavity, so that a hollowed, depressed area is formed in the center of the shielding grating. This makes it possible to produce airflow assemblies with a compact design and in small dimensions, since, for example, the hub of the fan or parts of the fan come to rest in the depression formed in the shielding grating.
Additional advantageous refinements of the unit of the invention are the objects of the dependent claims.
The invention is explained in greater detail below with reference to the embodiments illustrated in the attached drawings.